1. Field of the Invention
The present invention relates to a vehicle speed calculator for calculating vehicle speed by shooting a road surface, and to a vehicle including the same. More particularly, the present invention relates to a vehicle speed calculator which provides improved calculation accuracy of vehicle speed even when there is a change in vehicle height, and to a motorcycle including the same.
2. Description of the Background Art
There is known technique for shooting a road surface with a camera attached to a vehicle so as to measure a traveling speed and angle of the road surface relative to the camera and use them as vehicle speed and posture information.
For example, the Japanese Patent Laid-Open No. 2007-278951 discloses an approach for projecting a grid-shaped mark onto a road surface and shooting the projected grid-shaped mark with a camera so as to detect the vehicle speed, posture and other information based on the size and change of the grid-shaped mark.
However, the grid-shaped mark projected onto a road surface undergoes a change, for example, in width with change in vehicle height, making it likely that an error will occur at the time of conversion of the traveling speed of feature points obtained by optical flow into vehicle speed.
The present invention has been made to overcome such drawbacks of the existing vehicle speed calculator. Accordingly, it is one of the objects of the present invention to provide a vehicle speed calculator that offers improved calculation accuracy of vehicle speed even in the event of a change in vehicle height.